January 25, 2019

Consuming leafy greens like spinach and lettuce, red and dark orange vegetables, berries and orange juice may be good for the brain and help keep the memory sharp in old age, at least in men. Those are the results of a new study that followed a group of more than 27,000 men over two decades.

“One of the most important factors in this study is that we were able to research and track such a large group of men over a 20-year period of time, allowing for very telling results,” said study author Changzheng Yuan of the Harvard T.H. Chan School of Public Health. The findings, which appeared in the journal Neurology, “provide further evidence dietary choices can be important to maintain your brain health,” Dr. Yuan said.

The findings add to a growing body of evidence that a diet rich in fruits and vegetables, which is often recommended for heart health, may also be good for the brain. Vegetables and fruits are high in nutrients known to protect the brain and nervous system such as antioxidants. Earlier studies have found, for example, that older men and women who eat lots of fruits and vegetables tend to have less brain loss, which may protect against Alzheimer’s and other forms of dementia.

For the current study, researchers looked at 27,842 men whose average age was 51 at the start of the study. Participants were doctors, dentists, veterinarians and other health professionals who filled out initial questionnaires about how many servings of fruits, vegetables and other foods they had, on average, each day. They repeated the questionnaires every four years for up to 20 years.

Participants also underwent assessments of their thinking and memory skills at least four years before the end of the study, when their average age was 73. For the test, they were asked six questions:

* Do you have more trouble than usual remembering recent events?

* Do you have more trouble than usual remembering a short list of items, such as a shopping list?

* Do you have trouble remembering things from one second to the next?

* Do you have any difficulty in understanding things or following spoken instructions?

* Do you have more trouble than usual following a group conversation or a plot in a TV program due to your memory?

* Do you have trouble finding your way around familiar streets?

Answering “yes” to these questions indicates that someone feel that their memories might be slipping, a subjective assessment of memory loss. A poor test result can be an early sign of mild cognitive impairment, or MCI, a condition that more often than less progresses to full-blown Alzheimer’s disease.

According to the cognitive test results, 55 percent of the participants had good thinking and memory skills, 38 percent had moderate skills, and 7 percent had poor thinking and memory skills. 

The participants were divided into five groups based on their fruit and vegetable consumption. For vegetables, the highest group ate about six servings per day, compared to about two servings for the lowest group. For fruits, the top group ate about three servings per day, compared to half a serving for the bottom group.

A serving of fruit was considered one cup of fruit or half a cup of fruit juice. A serving of vegetables was considered one cup of raw vegetables or two cups of leafy greens.

The men who consumed the most vegetables were less likely to develop poor thinking skills than the men who consumed the least amount of vegetables. A total of 6.6 percent of men in the top group developed poor cognitive function, compared to 7.9 percent of men in the bottom group.

Leafy greens as well as red and dark orange vegetables, which are rich in carotenoid plant pigments that protect cells against oxidative damage (a form of chemical attack), were particularly protective. Such vegetables include tomatoes, carrots, yams, sweet potatoes, squash, kale, lettuce and red-orange peppers. Berries, such as strawberries and blueberries, also seemed to offer extra protection.

Daily orange juice consumption was also tied to better memory and thinking skills, particularly among the oldest men. A total of 6.9 percent of men who drank orange juice every day developed poor cognitive function, compared to 8.4 percent of men who drank orange juice less than once a month. Those reductions were not true for other juices like apple or prune juice.

The study does not prove cause and effect, and the effects were fairly modest. It only shows an association between consuming fruits and vegetables and reductions in memory loss. Food studies are difficult to control, and many people who eat healthy foods are also more likely to participate in healthy lifestyle measures like regular exercise.

Many factors determine who ultimately develops Alzheimer’s disease, including genes and your age. But the findings do suggest that a heart-healthy diet rich in fruits and vegetables is also helping to keep our brain fit, regardless of age.

By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Marc Flajolet, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.

Source: Changzeng Yuan, ScD; Elinor Fondell, PhD; Ambika Bhushan, MD; et al: “Long-Term Intake of Vegetables and Fruits and Subjective Cognitive Function in US Men.” Neurology, November 20, 2018